My wife and I towed the Base Camp (now named "Amelia") from New Jersey to my mother's house in Billerica, Massachusetts for Thanksgiving (about 300 miles one-way). It wasn't a camping trip, but Mom (a long time camper) wanted to see the baby so we hitched her up and went.
Our gas mileage was fantastic! 15.25MPG. The last time we drove that route, we got 15MPG, so I can only assume that our TV either didn't notice that the Base Camp was there, or my driving a lot more conservative because the Base Camp was behind me.
Being realistic, I did try to keep my speeds to the 65MPH limit, with occasional incursions into the 70-75MPH range (read that as "downhill"). When being passed by tractor trailers, I didn't notice any trailer sway at all. We loaded the tarioler as if we were going camping, so I think it's reasonable to expect that we'll get similar mileage when we take her out "for real".
The Base Camp does turn heads. Every time we stopped, we had people asking what it was and if they could have a look inside.
We stopped at Campers Inn in Merrimack, New Hampshire to pick up some accessories - the most important of which is an 11 gallon portable gray water tank. Airstream would do well to include one with the trailer.